We are studying the molecular biochemistry and fine structure of DNA repair. This includes work on the regulation and the mechanism of gene specific repair and transcription-repair coupling. We are studying DNA repair coupling with transcription with a view to clarify which gene products are involved and how these processes are regulated as compared to the DNA repair processes in the general, overall bulk of the genome. We use different approaches to the study of the regulation of gene specific DNA repair. They include the use of specific enzyme inhibitors, antisense systems, mutant cell lines, cell lines transfected with specific repair genes, fluorescence microscopy, and in vitro DNA repair assays. There are distinct differences in the efficiency of gene- and strand specific DNA repair dependent upon the type of DNA damage, and it is possible that the local degree of chromosomal distortion is the important element in determining the repair response chosen by the cell. We are suggesting that proficient DNA repair is necessary to secure genomic stability, and we find that certain regions of the genome that undergo translocation or rearrangements are poorly repaired.